| Electrical traction and drive system is the power source of the EMUs, and its control strategies, especially the control strategy of motor-side system, play an important role during that process of research and manufacturing localization & self-reliant of the key technology in high-speed EMUs in China. With the goals and requirements of steady-fast-accurate motor torque and speed response followed with command, low torque vibration, small motor body shaking, noise and heating, high efficiency, and low inverter switching loss, the electric motor control and inverter modulation strategies should satisfy, and play a great role on the train operation performance, such as safety, reliability and passengers’comfort. Thus, in whole speed operation range of electrical traction drive system, these methods to improve performances of motor torque, speed, stator current harmonic values and inverter switching operation, are really important and significant in theory study and engineering application. The detail contents of this paper are shown as:First of all, several basic theories of inverter control are introduced, such as mathematical modeling of three phase two-level inverter, mathematical relationships of inverter switch states & space voltage vectors, and asynchronous modulation algorithm of inverter. Then, three-phase asynchronous motor mathematical model and its indirect rotator field oriented control strategy are discussed.Secondly, referring to the space vector synthesizing method of asynchronous modulation algorithm, the two-level inverter multi-section synchronous space vector pulse-width-modulation (SVPWM) theory is extended for the application of medium-speed range. On the basis of that, the mathematical relation between voltage vector selection and stator flux locus is derived. And five kinds of none-zero voltage vector sequences with the corresponding motor stator flux locus are proposed for the inverter in the medium-speed range.Thirdly, on the basis of voltage-second balance principle, quantitative analysis is carried out for the internal relationship between the above five voltage vector sequences & the duty cycles of none-zero voltage vectors, the motor stator flux locus amplitude, and the torque steady-state value. And the duty cycle scheduling scheme of none-zero voltage vectors is designed in the case of keeping stator flux amplitude and stead-state torque constant, while the multi-section synchronous modulation changes one mode to another. Then, in order to achieve the minimum content value of stator current harmonics and optimize the duty-cycles of none-zero vectors, the mathematic expression of stator current harmonic contents with stator flux locus and the duty-cycle schedule of vectors is qualitatively analyzed for three kinds of stator flux locus modes. Furthermore, the duty-cycle schedule scheme of zero voltage vectors and the stator flux locus are optimized to achieve the minimum stator current harmonic value. On the basis of that, the effect of zero-voltage vector on torque ripple is discussed. In order to achieve the minimum torque ripple, the mathematic expression between zero-voltage vector and torque ripple is qualitatively analyzed. Furthermore, the multi-mode SVPWM strategy base on stator flux track design is proposed to achieve the minimum stator current harmonic value and torque fluctuation value. And the switching scheme between different modulation modes is shown then.Finally, hardware in the loop (HIL) experiment platform with OP5600/RT-LAB simulator and TMS320F2812 digital signal processor is set up. The main circuit model of electrical traction and drive system at motor-side is loaded into OP5600/RT-LAB simulator, and the proposed multi-mode SVPWM strategy of inverter and indirect rotator field oriented control of motor is programmed and loaded into DSP TMS320F2812. The validity and effectiveness of the multi-mode SVPWM algorithm are both verified by the simulation and HIL experiment results. |
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